An improved measurement of $\hat{I}{\cdot }^{\prime }\to e^{+}{e}^{-}\ddot{I}‰$

BESIII Collaboration, M. Ablikim, M. N. Achasov +772

Using a sample of $(10087\pm 44)\times 10^6$ $J/\ddot{I}ˆ$ events collected with the BESIII detector, an improved measurement of the decay $\hat{I}{\cdot }^{\prime }\to e^{+}{e}^{-}\ddot{I}‰$, with…